High efficiency and broad bandwidth terahertz vortex beam generation based on ultra-thin transmission Pancharatnam-Berry metasurfaces

• 作者: Wenyu Li Guozhong Zhao Tianhua Meng Ran Sun Jiaoyan Guo
• 来源期刊: 中国物理B（英文版）
• 年，卷（期）: 2021,（5）
• 所属期刊栏目: INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
• 页码范围: 753-759
• 页数: 7页
• 语种: 英文
• DOI: 10.1088/1674-1056/abd75c

摘要

The terahertz (THz) vortex beam generators are designed and theoretically investigated based on single-layer ultra-thin transmission metasurfaces.Noncontinuous phase changes of metasurfaces are obtained by utilizing Pancharatnam-Berry phase elements,which possess different rotation angles and are arranged on two concentric rings centered on the origin.The circularly polarized incident THz beam could be turned into a cross-polarization transmission wave,and the orbital angular momentum (OAM) varies in value by l(h).The l values change from ±1 to ±5,and the maximal cross-polarization conversion efficiency that could be achieved is 23％,which nearly reaches the theoretical limit of a single-layer structure.The frequency range of the designed vortex generator is from 1.2 THz to 1.9 THz,and the generated THz vortex beam could keep a high fidelity in the operating bandwidth.The propagation behavior of the emerged THz vortex beam is analyzed in detail.Our work offers a novel way of designing ultra-thin and single-layer vortex beam generators,which have low process complexity,high conversion efficiency and broad bandwidth.